GB638143A - Directive antenna arrangements, particularly for use in radio direction finders - Google Patents

Abstract

638,143. Radio aerials and direction-finding. STANDARD TELEPHONES & CABLES, Ltd. Oct. 11, 1946, No. 30401. Convention date, June 27, 1945. [Class 40 (vii)] A directive radio antenna arrangement comprises a single-turn, closed loop, conductor, a goniometer located at the geometric centre of the loop and a plurality of linear conductors separately connecting said goniometer to respective symmetrically spaced points on said loop. Preferably the linear conductors are connected to equally spaced points. A circular horizontal closed loop aerial 1 of diameter preferably less than a quarter wavelength at the mean frequency of the operating band is connected at equally spaced points by horizontal conductors 2-5 to a goniometer 11 mounted at the centre of the system. This goniometer may be of any type, but is described as similar to that of Specification 625,287. The output of the rotor of the goniometer may be connected to a direction-finding receiver feeding a signal amplitude indicator. Movement of the rotor rotates the figure of eight pattern of the system for direction finding. If left unscreened conductors 2 and 4, 3 and 5, may act as dipoles if the wavelength is short enough, the pattern of the dipole being the same as that of the loop so that the directional properties of the system are not affected. At longer wavelengths it is preferred to screen the conductors by tubular shields 32 connected to the casing 33 shielding the goniometer and having circular end plates 34 attached to their outer ends. The number and spacing of the conductors may be varied, e.g. there may be three equally spaced conductors, Fig. 4 (not shown). Likewise, rectangular or square loops may be employed. Fig. 5 shows a square loop 38 formed by the inner conductors of four coaxial lines, the outer sheaths of which are spaced apart at the corners of the square. Further coaxial lines 44-47 are connected to the mid-points of the sides and their inner conductors are attached to the loop at one end and to a goniometer at their other ends. This embodiment is stated to discriminate sharply against downwardly directed waves such as those reflected from the ionosphere.